NTP recurring

Answered Question
Mar 19th, 2010

Hi  All,

Please help me to understand the situation and solve it 

My devices start to run on BST  two weeks earlier that it actually DST starts on Sunday, 28 March 2010, 01:00 local standard time DST endson Sunday, 31 October 2010, 02:00 local daylight time. The device is synchronized with 127.127.7.1 what is this IP and why it has considered it as Sync master


Swtich6500#sh run | in cloc
clock timezone gmt 0
clock summer-time bst recurring
Swtich6500#sh run | in ntp
ntp master
ntp server 10.49.112.33
ntp server 10.49.112.34
Swtich6500#sh clock
15:53:25.263 bst Fri Mar 19 2010
Swtich6500#sh ntp ass

      address         ref clock           st  when      poll r  each  delay  offset    disp
*~127.127.7.1      127.127.7.1       7    16          64     377     0.0    0.00     0.0
~10.49.112.33     0.0.0.0            16     -           1024    0     0.0    0.00  16000.
~10.49.112.34     0.0.0.0            16     -           1024    0     0.0    0.00  16000.
* master (synced), # master (unsynced), + selected, - candidate, ~ configured
Swtich6500#sh ntp status
Clock is synchronized, stratum 8, reference is 127.127.7.1
nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is 2**24
reference time is CF4E0E60.EA4EBF4A (15:53:20.915 bst Fri Mar 19 2010)
clock offset is 0.0000 msec, root delay is 0.00 msec
root dispersion is 0.02 msec, peer dispersion is 0.02 msec
Swtich6500#sh clock de
15:54:02.975 bst Fri Mar 19 2010
Time source is NTP
Summer time starts 02:00:00 gmt Sun Mar 14 2010
Summer time ends 02:00:00 bst Sun Nov 7 2010

The device config which is acting as NTP master to the above mentioned device:-

CoreSwtich#sh run | in clock
clock timezone gmt 0
clock summer-time bst recurring
ntp clock-period 17179923
CoreSwtich#sh clock de
16:07:53.856 bst Fri Mar 19 2010
Time source is NTP
Summer time starts 02:00:00 gmt Sun Mar 14 2010
Summer time ends 02:00:00 bst Sun Nov 7 2010
CoreSwtich#sh run | in ntp
ntp clock-period 17179923
ntp source Loopback0
ntp master
ntp server X.X.X.101
ntp server X.X.X.100
ntp server X.X.X.102
CoreSwtich#sh ntp ass

      address         ref clock            st  when  poll reach  delay  offset    disp
+ 10.200.0.36      10.49.110.12      4    868  1024  377    -9.2  -73.35    31.7
~127.127.7.1      127.127.7.1        7      1    64     377     0.0    0.00     0.0
- 10.54.99.11      10.49.110.12       4    935  1024  377   -13.4  -101.6    51.8
* ~X.X.X.101       X.X.X.132            3     711  1024  377     4.5  -86.51    37.4
+ ~X.X.X.100       X.X.X.252            3    260  1024  377     1.8   11.23   136.3
+ ~X.X.X.102       X.X.X.106            3    720  1024  377     1.9  -24.32    28.2
* master (synced), # master (unsynced), + selected, - candidate, ~ configured
CoreSwtich#

Thanks

Jagdev

Correct Answer by Ganesh Hariharan about 6 years 11 months ago

Hi

Thanks for your help, I got idea why it has change on 14 March because in American Region it changing on DST started on Sunday, 14 March 2010, 02:00 local standard time DST ends on Sunday, 7 November 2010, 02:00 local daylight time Most of North America Springs Forward March 14, 2010 .

where as my device are situated in London, UK.

I need some more help why it has synced with 127.127.7.1 where as the device which is serving as master is working fine and it just next hope.

Regards

Jagdev

Hi Jagdev,

For your question why it gets synced with 127.127.7.1 is because  “127.127.7.1” is the internal server created by ntp master command, which the local router synchronizes to and in your first post if you see in your switch you have configured as ntp master under ntp configuration.

Hope to Help !!

Remember to rate the helpful post

Ganesh.H

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milan.kulik Fri, 03/19/2010 - 08:35

Hi,

the command reference guide (http://www.cisco.com/en/US/docs/ios/netmgmt/command/reference/nm_03.html#wp1013813 ) says"

"If the clock summer-time zone recurring command is specified without parameters, the summer time rules default to United States rules."

Which is your case, I'm afraid, "bst" is just a "Name of the time zone (for example, "PDT" for Pacific Daylight Time) to be displayed when summer time is in effect. The length of the zone argument is limited to 7 characters.", as the guide says.

HTH,

Milan

jagdev.dhaliwal Fri, 03/19/2010 - 23:38

Hi

Thanks for your help, I got idea why it has change on 14 March because in American Region it changing on DST started on Sunday, 14 March 2010, 02:00 local standard time DST ends on Sunday, 7 November 2010, 02:00 local daylight time Most of North America Springs Forward March 14, 2010 .

where as my device are situated in London, UK.

I need some more help why it has synced with 127.127.7.1 where as the device which is serving as master is working fine and it just next hope.

Regards

Jagdev

Correct Answer
Ganesh Hariharan Sat, 03/20/2010 - 08:19

Hi

Thanks for your help, I got idea why it has change on 14 March because in American Region it changing on DST started on Sunday, 14 March 2010, 02:00 local standard time DST ends on Sunday, 7 November 2010, 02:00 local daylight time Most of North America Springs Forward March 14, 2010 .

where as my device are situated in London, UK.

I need some more help why it has synced with 127.127.7.1 where as the device which is serving as master is working fine and it just next hope.

Regards

Jagdev

Hi Jagdev,

For your question why it gets synced with 127.127.7.1 is because  “127.127.7.1” is the internal server created by ntp master command, which the local router synchronizes to and in your first post if you see in your switch you have configured as ntp master under ntp configuration.

Hope to Help !!

Remember to rate the helpful post

Ganesh.H

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